tmpnam(3)



TMPNAM(3)                  Linux Programmer's Manual                 TMPNAM(3)

NAME
       tmpnam, tmpnam_r - create a name for a temporary file

SYNOPSIS
       #include <stdio.h>

       char *tmpnam(char *s);
       char *tmpnam_r(char *s);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       tmpnam_r()
           Since glibc 2.19:
               _DEFAULT_SOURCE
           Up to and including glibc 2.19:
               _BSD_SOURCE || _SVID_SOURCE

DESCRIPTION
       Note:  avoid  using  these  functions; use mkstemp(3) or tmpfile(3) in-
       stead.

       The tmpnam() function returns a pointer to a string  that  is  a  valid
       filename,  and  such  that  a file with this name did not exist at some
       point in time, so that naive programmers may think it a  suitable  name
       for  a  temporary file.  If the argument s is NULL, this name is gener-
       ated in an internal static buffer and may be overwritten  by  the  next
       call  to tmpnam().  If s is not NULL, the name is copied to the charac-
       ter array (of length at least L_tmpnam) pointed to by s and the value s
       is returned in case of success.

       The  created  pathname has a directory prefix P_tmpdir.  (Both L_tmpnam
       and P_tmpdir are defined in <stdio.h>, just like the TMP_MAX  mentioned
       below.)

       The tmpnam_r() function performs the same task as tmpnam(), but returns
       NULL (to indicate an error) if s is NULL.

RETURN VALUE
       These functions return a pointer to a  unique  temporary  filename,  or
       NULL if a unique name cannot be generated.

ERRORS
       No errors are defined.

ATTRIBUTES
       For  an  explanation  of  the  terms  used  in  this  section,  see at-
       tributes(7).

       +-----------+---------------+--------------------------+
       |Interface  | Attribute     | Value                    |
       +-----------+---------------+--------------------------+
       |tmpnam()   | Thread safety | MT-Unsafe race:tmpnam/!s |
       +-----------+---------------+--------------------------+
       |tmpnam_r() | Thread safety | MT-Safe                  |
       +-----------+---------------+--------------------------+
CONFORMING TO
       tmpnam(): SVr4, 4.3BSD, C89,  C99,  POSIX.1-2001.   POSIX.1-2008  marks
       tmpnam() as obsolete.

       tmpnam_r()  is  a nonstandard extension that is also available on a few
       other systems.

NOTES
       The tmpnam() function generates a different  string  each  time  it  is
       called,  up to TMP_MAX times.  If it is called more than TMP_MAX times,
       the behavior is implementation defined.

       Although these functions generate names that are difficult to guess, it
       is nevertheless possible that between the time that the pathname is re-
       turned and the time that the program opens it,  another  program  might
       create  that  pathname  using open(2), or create it as a symbolic link.
       This can lead to security holes.  To avoid such possibilities, use  the
       open(2)  O_EXCL  flag  to  open  the  pathname.  Or better yet, use mk-
       stemp(3) or tmpfile(3).

       Portable applications that use threads cannot call tmpnam() with a NULL
       argument  if  either  _POSIX_THREADS or _POSIX_THREAD_SAFE_FUNCTIONS is
       defined.

BUGS
       Never use these functions.  Use mkstemp(3) or tmpfile(3) instead.

SEE ALSO
       mkstemp(3), mktemp(3), tempnam(3), tmpfile(3)

COLOPHON
       This page is part of release 4.16 of the Linux  man-pages  project.   A
       description  of  the project, information about reporting bugs, and the
       latest    version    of    this    page,    can     be     found     at
       https://www.kernel.org/doc/man-pages/.

                                  2017-09-15                         TMPNAM(3)

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